Iran, at odds with Western governments over its nuclear program, has accused US and Israeli agents of being behind the killing.

"Any terrorist action or assassination of any people, whether scientist or civilian, is to be condemned. It is not acceptable. Human rights must be protected," UN spokesman Eduardo del Buey quoted Ban as saying.

He said the UN chief was speaking to media accompanying him on a trip to Lebanon.

Earlier this week, Iran's UN Ambassador Mohammad Khazaee sent a letter to Ban and the UN Security Council urging them to condemn the latest assassination, which it described as an act of terrorism.

UN diplomats said the 15-nation Security Council was unlikely to take up the issue and condemn the killing.

The murder of Ahmadi-Roshan was the fifth daylight attack in two years
on technical experts involved in Iran's nuclear program, which Western
countries believe is aimed at producing an atomic weapon but Tehran says
is for peaceful purposes.

The United States has denied involvement in the killing and condemned it. Israel has declined to comment.